Weight loss is the treatment of choice for obese patients with non-insulin dependent diabetes mellitus (NIDDM), but most adult diabetics do not adhere to a diet and do not lose sufficient weight. The application of behavioral techniques to problems of adherence may enhance the results of weight control programs for patients with NIDDM. Two studies are proposed in the development of a behavioral weight control program for adults with NIDDM. In the first study, the short- and long-term weight losses achieved in a behavioral treatment program will be compared to a nutrition education program, and a waiting list control. The effect of weight loss on blood pressure, serum lipid levels (cholesterol, triglycerides, and HDL cholesterol) and various parameters of blood sugar control (HbAlc, fasting blood sugar and fasting insulin) will be assessed. The second study will apply contingency contracting procedures to the treatment of patients with NIDDM and will determine whether it is more effective to target weight loss, reductions in blood sugar, or both changes simultaneously. Contingency contracting procedures have been used successfully in the treatment of obesity but have not yet been applied to the treatment of diabetics.